From f535a607c13c7b674e0788ca5765779aa74a01c3 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Tue, 22 Nov 2011 20:43:02 -0800 Subject: rcu: Eliminate RCU_FAST_NO_HZ grace-period hang With the new implementation of RCU_FAST_NO_HZ, it was possible to hang RCU grace periods as follows: o CPU 0 attempts to go idle, cycles several times through the rcu_prepare_for_idle() loop, then goes dyntick-idle when RCU needs nothing more from it, while still having at least on RCU callback pending. o CPU 1 goes idle with no callbacks. Both CPUs can then stay in dyntick-idle mode indefinitely, preventing the RCU grace period from ever completing, possibly hanging the system. This commit therefore prevents CPUs that have RCU callbacks from entering dyntick-idle mode. This approach also eliminates the need for the end-of-grace-period IPIs used previously. Signed-off-by: Paul E. McKenney Signed-off-by: Paul E. McKenney --- kernel/rcutree.h | 3 --- 1 file changed, 3 deletions(-) (limited to 'kernel/rcutree.h') diff --git a/kernel/rcutree.h b/kernel/rcutree.h index ea32405177c9..70d8a557090f 100644 --- a/kernel/rcutree.h +++ b/kernel/rcutree.h @@ -88,7 +88,6 @@ struct rcu_dynticks { /* Process level is worth LLONG_MAX/2. */ int dynticks_nmi_nesting; /* Track NMI nesting level. */ atomic_t dynticks; /* Even value for idle, else odd. */ - int wake_gp_end; /* A GP ended, need to wake up CPUs. */ }; /* RCU's kthread states for tracing. */ @@ -469,7 +468,5 @@ static void rcu_yield(void (*f)(unsigned long), unsigned long arg); static void rcu_cpu_kthread_setrt(int cpu, int to_rt); static void __cpuinit rcu_prepare_kthreads(int cpu); static void rcu_prepare_for_idle(int cpu); -static void rcu_wake_cpus_for_gp_end(void); -static void rcu_schedule_wake_gp_end(void); #endif /* #ifndef RCU_TREE_NONCORE */ -- cgit v1.2.3